The announcement answers some of the questions behind WhatsApp's recent purchase by Facebook for a price of 19 billion U.S. dollars.
Addressing the opening day of the Mobile World Congress in Barcelona, WhatsApp founder and chief executive Jan Koum confirmed the aim was to introduce voice calls, initially on the iPhone and Android.
Windows Phones and BlackBerrys will be included at a later date.
"We are adding voice to WhatsApp so that people can stay in touch with friends and loved ones no matter where they are in the world," said Koum.
"WhatsApp will continue to function as if it is an independent company without adding to its small staff of just 55 employees as the intention is for it to be able to remain as adaptable as possible," he said.
WhatsApp Messenger is a cross-platform mobile messaging application which allows people to exchange messages without having to pay for short message service, according to the company's website.